NullPointerException in PreparedStatement...

[Rajkumar balakrishnan]

Hi,
Things looking weird in Java, Yes, Ofcourse when i run this code yesterday it works fine and now it shows me a NPE on the PreparedStatement line.. Here is my code...

: Edited :

[Paul Sturrock]

So "con" is null. Where is is set?
[ July 23, 2008: Message edited by: Paul Sturrock ]

[Rajkumar balakrishnan]

The con is set in dbmodel.java and i extends that file with this file inorder to access the DB methods such as Statement, PS and con etc....

[Paul Sturrock]

...and how/when is it set? Something is going wrong with how you use it. Either there has been a problem establishing a connection (are there any stacktraces?) or you are using it incorrectly (e.g. there is an open connection step you are missing).

[Rajkumar balakrishnan]

Here is the stackTrace of errors...

java.lang.NullPointerException
        at com.rajk.javacode.servlets.LoginModel.checkSession(LoginModel.java:20
8)
        at com.rajk.javacode.servlets.LoginServlet.doPost(LoginServlet.java:43)
        at javax.servlet.http.HttpServlet.service(HttpServlet.java:710)
        at javax.servlet.http.HttpServlet.service(HttpServlet.java:803)
        at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(Appl
icationFilterChain.java:290)
        at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationF
ilterChain.java:206)
        at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperV
alve.java:233)
        at org.apache.catalina.core.StandardContextValve.invoke(StandardContextV
alve.java:175)
        at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.j
ava:128)
        at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.j
ava:102)
        at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineVal
ve.java:109)
        at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.jav
a:286)
        at org.apache.coyote.http11.Http11Processor.process(Http11Processor.java
:844)
        at org.apache.coyote.http11.Http11Protocol$Http11ConnectionHandler.proce
ss(Http11Protocol.java:583)
        at org.apache.tomcat.util.net.JIoEndpoint$Worker.run(JIoEndpoint.java:44
7)
        at java.lang.Thread.run(Unknown Source)
Check Session:0 admin null null
Check Session1: admin 0 0 1216806108171 0
admin admin

[vedha vas]

Hi Rajkumar balakrishnan,

The problem is with the con.Con is null.
The connection is not estabilished thats why its throwing NPE.
Pl post the dbModel.java class also so that we can find out how you are estabilishing the connection.

[Paul Sturrock]

So that is your NullPointerException. Well, we already know what causes that: the variable "con" is null. If there are no other exception messages then we can assume you are doing something wrong how you use con. Can you show use the code where con is initialised?

[Campbell Ritchie]

Insert this line just before it:

System.err.printf("The con variable is not null: %b%n", con != null);

[Campbell Ritchie]

Oh, I had this page open for some time, and didn't realise you had so many useful replies before mine! Sorry.

[Rajkumar balakrishnan]

: Edited :

[Paul Sturrock]

So presumably you have actually called your connect() method before you call your failing method?

[vedha vas]

Hi Rajkumar balakrishnan ,

In the checkSession method, in the try part first call the valueBound(event) method after that start
with the code:
ps=con.prepareStatement(SQL2);
ps.setString(1,sname);

[Rajkumar balakrishnan]

Small mistake.....
Thanks for your reply....
Its the closing time for this thread...
Meet you in some other post...

Thanks for all ranchers....

[Paul Sturrock]

Originally posted by vedha vas:
Hi Rajkumar balakrishnan ,

In the checkSession method, in the try part first call the valueBound(event) method after that start
with the code:
ps=con.prepareStatement(SQL2);
ps.setString(1,sname);

You should not be calling these methods directly. DBModel implements HttpSessionBindingEvent so will be called when a session binding event occurs. Presumably the pattern is to open a single connection for a single user when their session is bound?

[Rajkumar balakrishnan]

Yes.... Ofcourse....Thats's right...